1. Field of the Invention
The present invention relates to a rolling element interference preventer for a guide device, such as a linear guide device having an continuous circulation path for rolling elements, a swing bearing, a ball screw, and a spline. The rolling element interference preventer prevents the rolling elements rolling at regular intervals within the continuous circulation path formed between a pair of bearing races from interfering with each other.
2. Description of the Related Art
In various rolling guide devices having a bearing, a linear motion or rotation of a pair of bearing races is enabled by use of the rolling motion of rolling elements consisting of balls or rollers carried between the bearing races. To reduce the frictional resistance by avoiding the contact between each rolling element and to produce the smooth motion by arranging each rolling element at predetermined position, it is common practice that a number of rolling elements are incorporated between bearing races, using a metallic retainer.
In the conventional guide device using the metallic retainer, since a cage has a number of pockets and rolling elements are put rotatably into these pockets, there is an advantage that the operation of incorporating a number of rolling elements into the guide device is facilitated. However, it is required to hold a number of rolling elements incorporated into the pockets of the cage not to fall off, resulting in a problem that it takes a lot of time to fabricate the cage itself.
Thus, to solve this problem, a ball interference preventer (rolling element interference preventer) for use in a guide device to prevent interference between each ball has been proposed. The endless guide device includes a track rail having a rolling path, a sliding board having a rolling groove mutually opposed to the rolling path and moving along the track rail, and a number of balls (rolling elements). With a load applied, the balls roll in a continuous circulation path formed between the rolling path of the track rail and the rolling groove of the sliding board. The ball interference preventer is composed of a flexible resin connector having an interposing portion interposed between each ball and a connecting portion for connecting between the interposing portions, and holding each ball in an arranged state and rollably. Thereby, many appreciable results were achieved including 1) attaining low noise and good sound quality by removing the metallic sound due to collision between the balls (low noise), 2) reducing the wear of ball and increasing the retention of grease (maintenance free for long term), 3) attaining excellent high speed by decreasing the relative friction velocity (high speed), and 4) smoothing the motion by greatly reducing the rolling fluctuation (sliding property) (JP-B-6-56181, JP-A-5-52217, JP-A-5-126149, JP-A-5-196036, JP-A-5-196037, and JP-A-9-14264).
By the way, thus structured ball interference preventer composed of the resin connector is immersed in, or subjected to grease, lubricating oil, or coolant in the environment where the preventer is incorporated in the circulation path for the rolling guide device. Also, the ball interference preventer undergoes actions such as bending, tension, compression, twisting, or contact friction with the ball at any time. When reciprocated in the circulation path at high speed, this ball interference preventer undergoes an operation of bending, tension and compression severely and repeatedly. Further, when the ball interference preventer composed of the resin connector is immersed in, or subjected to grease, lubricating oil, or coolant, it absorbs water and oil to swell, causing a circulation failure in the circulation path and ablation of the preventer, and degrading the durability, sliding property and wear resistance.
Therefore, the rolling element interference preventer composed of the resin connector is required to have the excellent chemical strength of oil resistance, water resistance, and chemical resistance to the grease, lubricating oil and coolant, in addition to the mechanical strength of durability, sliding property and wear resistance. In view of the life of the guide device, it is required to be so durable and resistant to wear as to run about 30,000 km or more, with small sliding resistance variation, as well as resistant to oil, water and chemicals.
Moreover, the rolling element interference preventer composed of the resin connector was not too problematical in that an unnatural load was applied only on a part of the resin connector during the use, because the minimum radius of curvature for the continuous circulation path formed in the guide device was relatively large, the ball was employed as the rolling element, and the shape of the resin connector was devised. In recent years, however, the guide device is demanded for smaller size and higher speed, and the roller is employed as the rolling element, resulting in a problem that the durability, wear resistance and sliding property may be impaired.